Packaging machines are known that integrate the various components necessary to fill and seal a container into a single machine unit. This packaging process, generally stated, includes feeding carton blanks into the machine, sealing the bottom of the cartons, filling the cartons with the desired contents, sealing the tops of the cartons, and then off-loading the filled cartons for shipping.
Many packaging machines require one or more linearly driven mechanisms that assist in the various packaging processes. One such mechanism is set forth in U.S. Pat. No. 4,712,665 to McDonald et al. The '665 patent illustrates a container lifting mechanism that includes a vertical tube actuator that is slidably mounted in bearings within a fixed sleeve. A second vertical tube actuator is slidably mounted in bearings within the first vertical tube actuator so as to have independent vertical movement relative thereto. Vertical linear movement of the carton is accomplished by hydraulic activation of the first and second vertical tube actuators.
Trends within the field of packaging machines point toward increasingly high capacity machines intended for rapid, continuous filling and sealing of a very large number of identical or similar packaging containers, e.g., containers of the type intended for liquid contents such as milk, juice, and the like. One such machine is disclosed in U.S. Ser. No. 08/190,546, filed Feb. 2, 1994. The '546 application discloses, among other things, a mandrel-less packaging machine that utilizes a carton having a gabled bottom that is first sealed and then compressed to form a bottom on which the carton may rest. This is opposed to the mandrel-formed bottoms of prior cartons.
The lifter mechanism of the '665 patent is generally unsuitable for use with the gable-bottom cartons used in the machine disclosed in the '546 application. Accordingly, a more efficient lifting mechanism is desirable.